Patent Ear-trunpet. 29 
soft substance from touching the inner metallic tube, other- 
wise its vibratory action would in a measure be checked. 
For instance, if you strike a glass tumbler or a bell, the 
ringing sound almost immediately ceases on bringing the 
hand in contact with the vibrating body. The construction 
of this trumpet, however, allows the vibrations produced. 
upon the inner tube by the pulses of the air to pass freely 
into the ear. Thus you will observe that in addition to the 
vibrations reflected into the ear through the medium of the 
air, we have those produced and transmitted by the sonorous 
inner metallic tube, and the sound is thereby strengthened. 
Sound is conducted by some sonorous metals about ten times 
quicker than through the air; but as the conducting power 
of the latter is at the rate of about eleven hundred (1,100) 
feet in a second, the difference in an instrument of this size 
would be imperceptible. It may not be necessary for the 
outer tube to be constructed of metal, probably any material 
strong enough to keep the remainder of the tubes apart, 
when joined at the smaller end, would be suitable. 
I believe this ear-trumpet will not assist all cases of deaf- 
ness ; for, as I have previously remarked, how variable may 
be the nature of deafness; so I have no doubt the adaptation 
of this or any other ear-trumpet will vary accordingly. 
In two cases of deafness this was tried without the 
persons deriving any greater benefit from it than from those 
ordinarily in use. On the other hand, others have tried it 
and assured me of its efficiency, of which I have had satis- 
factory evidence in the increased facility with which I could 
converse with them when using it. 
The stethoscope, though differently constructed, is on the 
same principle as the ear-trumpet. By its means the peculiar 
sounds emitted by the vibratory action of certain parts of 
the body are readily conducted to the ear. The sound 
transmitted is also strengthened by resonance, which the 
tube, passing up the centre of the stethoscope, produces. In 
this tube is introduced a metallic wire connected only at 
both ends of the instrument ; it is tightly drawn, and b 
its tension is rendered extremely sensitive to the slightest 
vibration. The sound received at the one end is imme- 
diately communicated to the wire, by which it is more 
rapidly conveyed to the ear than by the wood or the air in 
the tube, with this addition, the sound is greatly increased. 
Wood is an excellent conductor of sound; the difference, 
therefore, in the conducting power of these media must be 
